The researchers found that the key to producing a smooth wave was not whether a cell communicates in an excitatory or inhibitory way, but rather which cells it communicates with. A brain cell can talk to its immediate neighbors in what researchers call on-center communication, or it can skip over its immediate neighbors and talk to its neighbors’ neighbors. That kind of communication is called off-center.
Using the computer, the researchers modeled on-center and off-center inhibitory signals, and produced two very different wave patterns.
When the simulated neurons communicated an inhibitory signal to their immediate neighbors, the resulting wave was jerky and disjointed. When they communicated an inhibitory signal to cells beyond their immediate neighbors, the wave flowed smoothly, albeit much slower than a normal excitatory wave. An excitatory wave may travel as fast as 100 meters per second, while the inhibitory wave traveled only 0.6 millimeters per second.
Terman said that the computer simulations may give scientists clues as to how nervous system disorders such as epilepsy jumble communication signals in the brain, and how inhibitory signals can lead to smooth, synchronous waves like those the brain produces during sleep.
“One of our main motivations for studying this is sleep rhythms,” explained Terman. “As someone first drifts off to sleep, the network of neurons in their brain isn’t very synchronized. It breaks up into different groups, each firing in a different pattern. But as the person falls deeper into sleep, the patterns gradually grow more and more synchronized. We’re trying to understand how that happens.”
Terman speculated as to why smooth waves formed by inhibitory signals
should travel through neurons
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Contact: David Terman
Terman.1@osu.edu
(614) 292-5285
Ohio State University
26-Mar-1998